Lennard Zinn, Velonews. 

http://velonews.competitor.com/2014/07/bikes-and-tech/technical-faq/technical-faq-the-lifespan-of-latex-inner-tubes_333917

He brings in advice from Challenge and Vittoria reps.  The first item from Challenge is "lightly inflating the tube exactly to the point where it first forms its toroidal shape with no extra pressure".

The easy way to accomplish that precisely (and fast, no CO2, no pump require.): inflate the tube by mouth!  Works really well.  I E-mailed this to Zinn so we may see it in the future.

Of course there is the small risk of germs.,  And as we all know, germs, as small as they are, have weight.  We all know added weight is the number two enemy after only aerodynamic drag (and those germs may cause a little of that also).

Ben